Blog

“In physics, angular momentum is the rotational analog of linear momentum. Like linear momentum it involves elements of mass and displacement. Unlike linear momentum it also involves elements of position and shape. It is an important quantity in physics because it is a conserved quantity – the angular momentum of a system remains constant unless acted on by an external torque.” - wikipedia

The Gait Guys Podcast #101 launches later this week. Here is a tickler. On the podcast we delve a little into this article based on Angular Momentum. We are not physics guys, but we try to give this idea some critical thought. Chime in if you know more than us, we would love to hear your research backed thoughts.

“To most runners and coaches, running is a series of jumps, says Svein Otto Kanstad, a physicist and former competitive runner based in Volda, Norway. Gravity isn’t considered helpful, because its force is perpendicular to the direction a runner is moving. But this mindset neglects the concept of angular momentum, Kanstad says. Rather than thinking of running as a series of jumps – leaping off one foot and landing again on the other – runners should view their sport as a series of falls, aided by gravity, he says.” -Boyle

Read the Rebecca Boyle and Kanstad articles then watch the World Record race video by Michael Johnson. Study his leg turn over on the straight away as compared to his closest 2 competitors. Something is different. His steps are shorter, and it is difficult to determine, but is he doing what Kanstad is suggesting ?

As Rebecca Boyle suggests, “a runner’s hips rotate to bring each leg forward, he or she gains angular momentum. But most runners don’t make the best use of this. At the moment their leading leg hits the ground, the second leg is usually stretched out behind. In Kanstad’s revised gait, the second leg will already have rotated forward again before the leading leg hits the ground. By doing this, the runner’s centre of mass is tilted far forward allowing for more forward momentum, but the recovery leg is there to stop a fall.”

As Kanstad suggests in his research: “A theory is developed to determine the magnitude and nature of these effects of gravity, showing that more than 10% of the energy needed for running can be obtained from the field of gravity. Likewise, at a particular optimum velocity, walking may become entirely driven by gravity-induced angular momentum without any muscular effort.”

*Addendums (copied discussions from our Social media pages, we have smart people follow our work, so we wanted to include some dialogues here. We do not necessarily agree with everything said here, but in turn we also do not know everything. So, it is worthy of sharing in the hopes it takes us all further down the road to enlightenment).

reader: For some interesting applications and background on whole body angular momentum check out Anne Silverman’s work (Col School of Mines). There’s some interesting implications for how gait is regulated. Hope all is well. http://www.ncbi.nlm.nih.gov/pubmed/22325978

Gait Guys: Dear X, we very much appreciate your contributions and thoughts here. You seem to be a strong advocate of Romanov’s work. Can you furnish us with some of his research, we like to see the numbers and studies. His stuff has been around for awhile, certainly there has to be a few good papers you can lead us too to cut down our search to the good ones.

another reader: After reading this (original article) I didn’t know whether to laugh or cry! It’s still amazing to me the confusion and mayhem surrounding running gait mechanics. With Nicholas Romanov already establishing the idea of gravitational torque as the propulsive force in running, how can Kanstad’s “new ” belief be taken seriously: vis-a-vis the Pose Method being conceptualized during the 1970’s. It truly makes me wonder whether scientists, researchers or coaches are actually trying to understand the truth or just emblazon their own reputations. From Bobby McGee to Daniel Lieberman, the misinterpretation of how we move in a gravitational environment is profound. The idea that we can generate anti-gravitational force via muscular effort to generate movement has an almost ludicrous logic to it. The idea of “just run barefoot” or “take smaller strides” or “land of the midfoot” trivializes the unique hierarchical interplay at the core of all human movement.

As a Movement Specialist, former student of Dr. Romanov’s and someone with a passion for the history of biomechanics, the fundamental flaw is obvious: science observed human gait and tried to conjecture based on the idea of the human body being a machine, rather than the body as another biological system on this planet. The ideas of everyone from Aristotle to daVinci, Galileo to the Weber brothers concluded that the the body must move in harmony with nature. Perhaps it was the rush of modern civilization via the Industrial Age which signified a change in the scientific method. Whatever the specific catalyst, the onslaught of data collection as evidence was born.

Even today, with all of the technology available, the idea of the foot being a fulcrum for the body to rotate over, is lost. What’s even further not understood is that the body, as a lever arm, must be aligned properly - if not, the fall forward is interrupted and all of the mistakes taught in classical stride mechanics (push-off, drive, etc.) become common error. It’s ironic that Kanstad mentions Michael Johnson (who I agree ran with proper “pose"technique), but who even today, would describe his own form differently. Which is why Usain Bolt, the who does pretty much everything correctly, is still a scientific conundrum.

I can provide Pose-related research (though I suggest looking at the information in his Pose Triathlon book). But as you know, there are many contrary arguments and much conflicting information out there that is seemingly supported by data research as well. What I tried to elucidate is that it’s difficult to consistently quantify proper running technique. Research studies would have to be designed differently, the athletes trained for longer periods of time, acclimated to both normal ground and treadmill surfaces, freed from any musculoskeletal and psychological inhibitions to running better. With any athlete I work with, there is usually a period of (at least) a year’s time of training which must be performed: longer periods for endurance or injured athletes. Studies can try to isolate certain physical elements or characteristics of form: these clearly miss the perceptive and sensory aspects most critical to better form. Essentially what it always come down to is basic: where are you when your foot hits the ground, how long do you spend on the ground and what do you look like at terminal stance? If these concepts could be studied, then I’m all for it. Unfortunately, studies continue to observe and rely on the factorial by-products or results of error-filled running technique. In the end, who is deciding if the subjects are actually doing things well enough to warrant studying them?

another reader: As a PT I agree with Kanstad. While Michael Johnson appears to be fully upright, his chest and stomach are leaning forward. I’m willing to bet his COM is anterior to his trunk while he’s running. There’s probably some give and take though, just like anything else. Leaning too far forward will make you unsteady and you’ll end up slowing down to prevent a fall. Leaning too far backwards or even being vertically upright would, as Kanstad suggests, would prevent any angular momentum via gravity from assisting a runner, and would even work against them and push them backwards.